Integrating counter circuit



April 17, 1951 E. R. sHENK ET AL 2,549,022

INTECRATINC COUNTER CIRCUIT Filed Oct. 27, 1945 By 729 WM/V Arme/VFY Patented Apr. 17, 1951 IN TEGRATING COUNTER CIRCUIT .Eugene R. Shenk andrArthur E. Canfora., Brooklyn, N. Y., assignors to Radio Corporation of America, a corporation of Delaware Application October 27, 1945, Serial No. 625,084

.This invention. relates to integrating counter circuits and has for its principal object to provide a circuit arrangement which will count a series of pulses up to a certain predetermined number and while doing so will guard against the counting of spurious pulses or momentary line surges such as might otherwise result in an erroneous count.

Briefly described, our circuit arrangement for counting pulses is one in which the components are so chosen as to cause a certain amount of charge to be stored in acondenser, the total charge being an accumulation of successive charges which result from the application of a pulse train. The circuit arrangement is also provided with time constant components such as to require a denite time interval for each pulse to be counted. When the total charge reaches a predetermined amount, representing a denite number of pulses, a tube is rendered conductive.

Our invention will now be described in more detail, reference being made to the accompanying drawing the sole figure of which represents diagrammatically a preferred embodiment of the invention.

Referring to the drawing, we show input terminals I on which the pulses to be counted are impressed. These'input terminals are connected lrectification paths D1 and D2. The cathode of path D1 is grounded. The anode of this same path is connected through a resistor R3 toone 1 electrode of a charging condenser C1, the other electrode of the condenser C1 being connected to the anode P1 of tube 2.

Condenser C1 is also connected between the anode of tube 2 and a resistor R4 leading to the cathode of the rectication path D2. The anode of this path is connected to the anode of another rectier D3, whose cathode is grounded. In shunt with the rectifier D3 is a circuit including resisto R5 and a storage condenser C2.

For utilization purposes two discharge tubes 5 and 6 arranged in an aperiodic trigger circuit may be employed if desired. The cathode of tube 5 is connected to the anode of the rectifier path D3. The anode of tube 5 is fed with'direct current from source 4 across resistor Rv. The Vgrid G2 in tube 5 is connected to ground through a resistor Re. This grid is also directly connected to the anode in tube 6. A capacitive coupling. cir- 9 Claims. (Cl. Z50- 27) cuit between the anode of tube 5 of tube 6 includes condenser Ca. The grid G3 of tube 6 is returned to its cathode through. a resistor Rs. The cathode is connected to the negative terminal of the direct current source 1. Utilization of the tripping action .between tubes 5 and E may be obtained by the use of output terminals 8, one of which is grounded while the other is coupled to the anode of tube 5 through a capacitor Cr. i y 1 There are applications in which it is desirable that a predetermined minimum length of time be assigned to each pulse in order to reach a certain count. Such a device fullls a useful purpose in signal identification equipments or error.

detecting systems.

In carrying out our invention we have found it possible to provide circuit components which` are so coordinated as, to permit termination of the count on the start, or leading edge of the last pulse to be counted. In other words, if a count `of N steps is desired, then N.l of them require a predetermined minimum length of time` to accumulate, but the count terminates at the start rather than during or at the end of the Nth step. Y

. Operation of the Circuit In the following description of operation it will be 'observed that tube5 is rendered conductive only after a predetermined number of pulses has been injected into the' counter circuit. First let it be assumed that `the potential applied to the anode of tube 2 is that of the positiveterminal of source 4 due to the fact that tube 2 stands in" va non-conductive state. A positive pulse applied to the input terminals ofY tube 2 renders this tube conductive and the voltage, change on the anode is essentially a function of I1R1, where I1 represents the space current in tube'Z. Let 'it also be drop through resistor Rs under the condition that tube 6 is normally conducting.

The critical firing voltage to which C2 must be charged in order to render tube 5 conductive will 1 be indicated by -Ec.

AssumeI that we-wish tube 5 to conduct after three counts, 4the iirst two-being integrated.

The rst count: Grid Gris made positive and held sofor la minimumtime T. This causes a v01tagechangeon,theanode P1 equal to I1R1.

and the grid1 The cathode of tube 5 is` Condenser C1, normally charged to the terminal voltage of source 4, will assume a new voltage due to the potential drop through resistor R1 While tube 2 is conductive. Because of this, current will flow through a circuit which includes resistor R1, diode path D2, resistor R5 and condenser Cz. The diode path D3, as connected, prevents the discharge of condenser C2 and yet allows an electron path for the current which traverses tube 5.

There are two points to be noted in this action. First, the cathode of tube 5` is drivensomewhatnegative due to the potential drop across resistor R5. This condition is determined by the relative ohmic values of resistors R1 and R2 (the effective resistanceV of tube 2) and of resistors R4 and R5, the last two being interconnected through the diode path D2. The effective resistance R2 is usually small compared to R4 and R5. evident that placing Aa negative potential on the cathode of tube 5 is equivalent to placing a polsitive potential on the grid of tube 5.

Second, theactual step voltage placed on condenser Cz is reached after a time interval de# termined by the values of resistors R1, Rz, R4 and R5, and the effective condenser requal to Y CiC'z C14-C2 In between successive counting pulsesv the capacitor C1 must be restored to its original charge.

This is accomplished by driving the grid G1 negative so as to bias tube 2 to cutoff; The anode potential then rises to that of the terminal voltage of the source 4. The charging current through capacitor C1 now traverses resistor R3 and the diode path D1.V The charge previously.

condenser C2, however, is not doubled, as might erroneousl)r be assumed. The reason for this is that the effective change in voltage across the two condensers is no longer I1 R1, but I1 R1 minus'the step of voltage already on condenser Cz; The total C2 voltage at the end of the predetermined interval of the second count is O1 C', C, 01+CJRIJFG,+C2[IRC1+CJR1] The amplitude of the second pulse across resistor R5 is also smaller than the rst and becomes still smaller with each succeeding count just as each succeeding appliedstep voltage becomes smaller.

With proper design procedure, the first two counts apply a total voltage to condenser C2 which is less than V'the critical firing voltage -Ec. The rst step voltage plus the second initial pulse is alsoless than the critical ring voltage.

y The third count (assuming it to be nal) differs from the rst two in that it is not integrated. The initial pulse at the start of the count is of such amplitude that, superimposed on the total voltage already across condenser C2, it immediately drives the potential of the cathode Q1 1711170@ It Will be 4 5 more negative than the ring voltage. This being the case, tube 5 res, the trigger circuit trips and the object of the circuit is accomplished. When tube 5 res (becomes conductive), a positive potential is placed on the anode of diode D3 which also becomes conductive. This diode D3 thus provides the D. C. return path for tube 5.

In summation, the charge in flowing into condenser C2 must flow through resistors R5 and R4, hence producing a time delay (that is, requiring time) for the charge to build up on condenser C2. Hence, a short duration spurious pulse would add only a negligible charge to condenser C2l and would not eiect the counter. The condenser C2 integrates the current that flows into it through resistor'Rd, rectier D2, and resistor R5, and the'resistors slow up the charging of p condenservCZ. The values of resistors R4 and R5 depend upon the duration of the pulse it is desired to count. The longer the pulse to, be

counted the higher will be the values of resistors R4 and R5.

In place of the trigger circuit composed of tubes 5 and 6, a conventional locking circuit may just as well be activated after the desired number of counts.

Full integration on all counts is obtained mere-VVv ly by omitting R5 and compensating for itsabsence, as far as the time constant is concerned,

by increasing the value of resistor R4.

We claim:

l. An impulse counting system comprising .a'

rst electron discharge tube having an input circuit for receiving the impulses to be counted and an output circuit connected between its anode and cathode, said output` circuit including an anode circuit resistor and a direct current source; a first 1 capacitor and a second capacitor; a rst unilateral circuit extending from ground through the first tube, through the first capacitor, thence through two resistive elements and through the second capacitor to ground; a second unilateral circuit extending from ground through a third resistive element, through the first capacitoit through said anode circuit resistor and Vsaid source to ground; diode rectier meansfor Vrendering said unilateral circuits mutually opposed and conductive only as permitted by the polarity of potential differences along Ysaid circuits; and electronic means for dissipating the charge err said second capacitor after it has reached a criti-f cal potential, which potential results from the storage of incremental charges on said second.

minimized. Y

2. An impulse counting system according' `to claim 1 wherein said electronic means for dis-"f' sipating the charge on said second 4cap'acitor'i's i constituted as one of two discharge tubes inv aV locking circuit, which tubes are arranged 'for mutual interaction so that when one is rendered ,i

conductive the other is blocked, and vvice versa.4

3. An impulse counting system comprisinga rst electron discharge tube having input and'j output circuits, said input circuit being coupled`l` to a source of impulses tobe counted, a first capacitor constituting a common circuitconnecj tion between the ,anode 9i said tube and a pair of opposingly poled unilateral circuits which, together with said capacitor; are in shunt with said output circuit, each of-said unilateral circuits having` resistive impedance in series therewith suchthat in combination with said capacitor a certain time-constant is developed for acceptance ofV the impulses tobecounted andv for rejection of shorter duration spurious and transient pulses, a second capacitor and an additional resistor in series therewith in circuit with one of said unilateral circuits and having a certain time constant value, said second capacitor being arranged to store successive increments of charge thereon, and electronic means for discharging said second capacitor when said stored charge has reached a predetermined value corresponding to the number of impulses to be counted.

4. An impulse counting system according to claim 3 and including a diode rectifier in shunt with the circuit of said second capacitor and said additional resistor.

5. In an integrating counter circuit, two capacitors interconnected through resistive and rectifying means the circuits of which are completed through the space path of an electron discharge tube having an input circuit and an output circuit, said output circuit being external to the circuit components aforementioned, a second discharge tube coupled to a point between said two capacitors and constituting means for discharging the second of said capacitors after a predetermined number of incremental charges have been stored therein in response to the application of discrete pulses to said input circuit and thence to the rst of said capacitors, said. resistive means in association with said capacitors introducing a predetermined time delay for the building up of a charge on said second capacitor in response to an input pulse, said time delay being operative to nullify the counting effects of stray and spurious pulses applied to said input circuit which are of shorter duration than the pulses to be counted.

6. The method of counting pulses of electrical energy up to a predetermined number by the use cf an electronic circuit arrangement which possesses resistive and capacitive circuit components arranged to accumulate in a second capacitor a series of transient charges corresponding to individual charges momentarily stored in a rst capacitor, said method comprising rectifying the energy which is transferred from the rst to the second capacitor, dissipating by rectification the energy stored in the first capacitor, discharging the second capacitor through a certain portion of said electronic circuit arrangement only so often as said predetermined number of energy pulses is counted, and selecting the time constant characteristics of said resistive and capacitive circuit components so as to introduce a delay in the transfer path between the iirst and second capacitors, to thereby discriminate against the counting of stray and spurious energy pulses which are to be distinguished from the true pulses to be counted.

7. A pulse counting circuit of the type which comprises electronic means and associated input and output circuits for storing and discharging energy pulses in one condenser while accumulating corresponding charges in a second condenser up to one less than the number N of such pulses which are to be counted, said condensers having in series therewith a plurality of resistors separated by a unidirectional current passing device, Said resistors having such values as to introduce 6 a delay in the time required to build up a charge on" the second condenser, and means for terminating the counting operationV at the start of the Nth pulse,` said means including adischarge tube the output circuit of which is connected through said second condenser for discharging the energy stored therein, andan input circuit se biased as to permit conductivity in said tube only after the charge in said condenser has been built up to a critical value by the initial increment of said Nth pulse.

8. In combination, a storage condenser, a charging condenser, the series circuit of a resistor, a unilaterally conducting device :and another resistor in the order named connected between one plate of each of said condensers for admitting current from said charging condenser to said storage condenser, the series circuit of a second resistor and a second unilaterally conducting device connected between the junction of the charging condenser and the rst-mentioned resistor and the other plate of said storage condenser for discharging said charging condenser, means to impress a pulsatling current between the other plate of the storage condenser and the other plate of the charging condenser, and means coupled across the storage condenser for discharging the storage condenser following a predetermined charge on said storage condenser, said last means comprising an electron discharge device having an anode, a cathode and a grid, a direct connection .from said cathode to the junction point of the unilaterally conduct-ing device and said other resistor of the first series circuit,` a direct current connection from the positive terminal of a source of unidirectional potential to said anode, a triggerV circuit coupled to said grid, and a diode having an anode directly connected to said cathode and having a cathode directly connected to said other plate of said storage condenser.

9. A pulse counting circuit comprising a vacuum tube having an anode and a cathode, a resistive circuit between said anode and the positive terminal of a source of unidirectional potential, a charging condenser and a storage condenser, the series circuit of a resistor and a unilaterally conducting device connected between one plate of each of said condensers for admitting current from said charging condenser to said storage condenser, the series circuit of a second resistor and a second unilaterally conducting device connected between the junction of the charging condenser and the rst-mentioned resistor and the other plate of said storage condenser for discharging said charging condenser, a direct connection between the other plate of said charging condenser and said anode, a connection between the other plate of said storage condenser and said cathode, means coupled to and causing said vacuum tube to conduct each time a `pulse is to be counted, another vacuum tube having an anode connected to said positive terminal and a cathode connected to said one plate of said storage condenser, and means for causing said last vacuum tube to conduct and discharge said storage condenser following a predetermined charge on said storage condenser, said last means including a rectifier coupled across said storage condenser through a resistor, one electrode of said rectifier being directly connected to the cathode of said last vacuum tube.

Y EUGENE R. SHENK.

ARTHUR E. CANFORA.

(References on following page) REFERENCES CITED VThe following references are of record in the le of this patent;

UNITED STATES PATENTS Number Number 8 Name Date Fitzgerald Mar. 1, 1938 White Apr. 5, 1938 Dimond Apr. 12, 1938 Sanders July 9, 1946 Schoenfeld Feb. 11, 1947 Busgnes Mar. 29, 1949 

